The rounded umami taste of savoury products produced by the food industry is often provided by combinations of monosodium glutamate (MSG), inosine monophosphate (IMP) and guanosine monophosphate (GMP), or yeast extracts or natural flavours. The common base of these umami providers is very often MSG, which can be produced by fermentation of Corynebacterium glutamicum strains and then purified, or is naturally occurring in some raw materials, such as meat, fish, breast milk, tomatoes, and parmesan cheese. Consumer perception of added MSG is generally negative in some countries, especially Germany, France and the US. There is therefore a need for alternative solutions to the problem of delivering umami flavour providers or enhancers.
The taste compounds in vegetables come from interactions between different sensory factors, either from carbohydrate storage compounds (especially mono- and disaccharides), the texture of the plant material provided by structural polymers, or from secondary metabolites. Taste compounds in vegetables also depend on growing conditions, storage, and the preparation and cooking methods used for the vegetables. Of the secondary metabolites, the terpenoids are the major contributors of taste and flavour, followed by glucosinolates, alkyl and alkenyl cysteine sulphoxides, and phenolic compounds. Individual terpenoids are perceived to have a wide range of flavours and aromas, which tend to blend into the characteristics of carrot. Enzymatic cleavage of glucosinolates produces the typical flavours and aromas of the Brassicas. Methyl cysteine sulphoxide also contributes to Brassica flavour, while the cleavage products of this and other alkyl or alkenyl cysteine sulphoxides produce the pungent and sulphurous flavours characteristics of alliums. Phenolic compounds generally produce bitter and astringent flavours, and have been detected in all groups of vegetables (Brückner B. and Wyllie G., 2008. Fruit and vegetable flavor. Recent advances and future prospects. Woohead Publishing, 2, 11).
During blanching or cooking of vegetables, taste active ingredients dissolve in the water. This water is typically discarded, which can cause environmental problems due to the high chemical oxygen demand of the dissolved compounds.
Many techniques have been repeatedly used to extract and concentrate taste and aroma molecules in food matrices. In culinary art concentration is mostly done by reduction. Membrane technology is one of the earliest successful industrial applications of technology in this field (Sano, C. 2009, American Journal of Clinical Nutrition. 90:3, 728s-732s). The main use of reverse osmosis is the concentration of liquid foods, to complement or replace evaporation. Nanofiltration is used for desalting and de-acidification with partial concentration, while ultrafiltration is used for fractionation, concentration and purification of food streams. Microfiltration is used for clarification and removal of suspended matter to replace centrifuges and filter presses, and also for pasteurising and sterilising liquids instead of using heat.
Known processes of concentrated mushroom blanching water are based on vacuum evaporation or steam jacket kettle concentration. Chiang et al. (1986, Journal of Food Science 51(3), 608-613) concentrated the blanch water to 13% of solids using ultrafiltration and reverse osmosis. Nonvolatile components like IMP and GMP were analyzed and 84% were recovered. These ribonucleotides were indicated to replace or enhance MSG. The major volatile compounds recovered were 1-octen-3-ol, 3-octanol, and 3-octanone. The aroma quality was evaluated by a sensory panel. No change in quality from blanching water to concentrate was detectable. The extraction of mushroom slices at different temperatures and subsequent ultrafiltration and reverse osmosis of the extract enables the aromas compounds to be recovered (Kerr, L. H. et al., 1985, Journal of Food Science 50, 1300-1305).
Tomatoes are rich in natural glutamic acid. EP 2068650 discloses the use of membrane technologies for removing lycopene and citric acid from a tomato concentrate, leading to a clear and tasteless tomato concentrate.
Seafood processing industries have used membrane filtration treatment since the 1970s to recover valuable peptides or proteins in defrosting, washing or cooking waters (Cros et al., 2005, Journal of Food engineering, 69, 425-436). This publication discloses the concentration of mussel cooking water to produce a natural aroma concentrate and a clean water stream. The production of aromatic concentrates from seafood cooking juices can be achieved using reverse osmosis, but the high salt content makes a preliminary desalination step necessary. Desalination with electrodialysis to reduce salt content by 85% is possible without significant aroma loss. Further desalination will lead to a change in the aroma profile, which is dependent on the membrane material (Cros et al., 2005, Desalination, 180, 263-269). Cooking water from buckies, shrimps and tuna with a high polluting load must be treated before being returned to the environment. Combinations of ultrafiltration and nanofiltration, as well as ultrafiltration and reverse osmosis were checked for their ability to recover flavours and to clean the waste water (Vandanjon, L. et al. 2002, Desalination 144, 379-385). Cooking juices from tuna processing have a high polluting load, including high chemical oxygen demand, high nitrogen content and large amounts of dry matter. A high NaCl load is also problematic (Walha, K. et al., 2009, Process Safety and Environmental Protection, 87, 331-335). Tuna cooking juices contain interesting fishy flavours. Highly salted tuna cooking juices can be concentrated by a one- or two-step nanofiltration. The flavour intensity of the juices can be decreased by nanofiltration, thereby modifying the aroma properties (Walha, K. et al., 2011, LWT—Food Science and Technology, 44, 153-157).
The principal disadvantage of the above known vegetable processing side streams for delivering an umami flavour is that the MSG present becomes concentrated during further processing and leads to an unacceptably high level of MSG in any flavouring composition prepared from it. The applicant has now found that vegetable cooking or blanching waters, which are side streams in the food industry, especially from pea or corn, can be concentrated by membrane processes and used as natural flavour solutions. In other words, the applicant has found a way to produce umami flavour compositions from vegetable extracts and vegetable side streams that does not concentrate the natural MSG present. The invention is based on the use of membrane technology and other concentration techniques like evaporation and reduction. Until now, membrane filtration technology has only been used for processing food processing side streams for waste water cleaning and desalination in the seafood industry, but not for obtaining a umami flavour.
It is therefore an object of the invention to provide an umami flavour composition obtained from vegetable processing side streams, or at least to provide an useful alternative to existing flavour compositions.